Structure design and analysis of tactile sensor. (a) Illustration of the dimensions of the tactile sensor and scanned Braille, and finite-element calculations show the deformation and the local stress distribution of tactile sensor when without dot on Braille, with one-side dot, and with two-side dots on Braille. (b) Finite-element calculations show the deformation and the local stress distribution of tactile sensor with no microstructure, micro-column, micro-pyramid, and micro-sphere. (c) Finite-element calculations show the deformation and the local stress distribution of micro-sphere tactile sensor with different distances.